Tillämpad programmering

Tillämpad programmering
Erlang IV
Johan Montelius
Tillämpad programmering ID1218
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Actor-modellen
{foo, 42}
{zot, 77}
{bar, 37}
Tillämpad programmering ID1218
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delat minne
Tillämpad programmering ID1218
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processer
●
Vi skapar en ny process med
–
spawn/3 eller
–
spawn/1
-spec spawn(module(), atom(), [any()]) -> pid().
-spec spawn(fun()) -> pid().
Tillämpad programmering ID1218
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spawn/3
-module(foo).
-export([init/1]).
init(State) ->
:
:
Tillämpad programmering ID1218
:
Pid = spawn(foo, init, [42]),
:
:
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spawn/1
-module(foo).
-export([start/1]).
start(State) ->
spawn(fun() -> init(State) end).
init(State) ->
:
:
Tillämpad programmering ID1218
:
Pid = foo:start(42)
:
:
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self/0
• Den inbyggda funktionen self/0
returnerar processens egen identifierare.
Tillämpad programmering ID1218
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att skicka ett meddelande
• Vi kan skicka vilken datastruktur som
helst.
hello(P) ->
P ! {hello, world}.
Tillämpad programmering ID1218
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receive
• En process tar emot ett meddelande
med receive.
waiting() ->
receive
{hello, X} ->
X;
bye ->
ok
end.
Tillämpad programmering ID1218
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process med tillstånd
-module(server).
-export([start/1]).
start(State) ->
spawn(fun() -> loop(State) end).
loop(State) ->
receive
{store, X} ->
loop(X);
stop ->
ok
end.
Tillämpad programmering ID1218
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process med tillstånd
loop(State) ->
receive
{store, X} ->
loop(X);
{tellme, Pid} ->
Pid ! {state, State},
loop(State);
stop ->
ok
end.
Tillämpad programmering ID1218
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process med tillstånd
test() ->
S = server:start(42),
S ! {store, 17},
S ! {store, 23},
S ! {tellme, ...},
receive
{state, X} ->
X
end.
Tillämpad programmering ID1218
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processes
Tillämpad programmering ID1218
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meddelanden
meddelandekö
(brevlåda)
Tillämpad programmering ID1218
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ordning på meddelanden
P1
P2
ta emot hantera
meddelanden
leveras i FIFO-orning
m1
inga ack:ar
m2
m2
m1
Tillämpad programmering ID1218
mottagaren bestämmer
vilka meddelanden som
skall hanteras
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när är ett meddelande leverat
:
S ! {store, 17},
:
:
S ! {store, 23},
:
:
Tillämpad programmering ID1218
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vilket meddelande hanteras
{tack, 4}
{tick, 3}
Tillämpad programmering ID1218
:
receive
{tick,
X
{tack,
X
end,
X} ->
+ 3;
X} ->
+ 4
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vilket meddelande hanteras
{tack, 4}
:
receive
{tick,
X
{tack,
X
end,
X} ->
+ 3;
X} ->
+ 4
{tick, 3}
Tillämpad programmering ID1218
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vilken ordning
src(End, Relay) ->
End ! a,
Relay ! b.
relay(End) ->
receive
X -> End ! X
end.
a
src
b
end
b
relay
Distributed Systems ID220U
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registrering
:
Pid = spawn(log, start, []),
register(log, Pid),
:
:
log ! {now, this, 42}
:
Distributed Systems ID220U
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varning - kan misslyckas
:
Pid = spawn(log, start, []),
register(log, Pid),
:
:
log ! {now, this, 42}
:
Distributed Systems ID220U
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processer med tillstånd
Processer är ett förbund
med djävulen!
Tillämpad programmering ID1218
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referencial tranparency
:
:
foo(X, Y, Z),
:
:
X = spwan(... ),
:
foo(X, Y, Z),
:
Tillämpad programmering ID1218
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process med tillstånd
-module(memory).
-export([new/0, read/1, write/2]).
new() -> spawn(fun() -> memory(0) end).
memory(State) ->
receive
{read, Pid} ->
Pid ! {ok, State},
memory(State);
{write, Val} ->
memory(Val)
end.
Tillämpad programmering ID1218
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process med tillstånd
read(Mem) ->
Mem ! {read, self()},
receive
{ok, Val} ->
Val
end.
write(Val, Mem) ->
Mem ! {write, Val},
ok.
Tillämpad programmering ID1218
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imperativ programmering :-0
:
Mem = memory:new(),
mem:write(15, Mem),
mem:write(32, Mem),
Val = mem:read(Mem),
:
Tillämpad programmering ID1218
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delat minne :-0
Tillämpad programmering ID1218
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rena funktionella moduler
funktioner
processer
Tillämpad programmering ID1218
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Finite State Machine (FSM)
take
foo
bar
closed
open
release
quit
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quit
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Finite State Machine
open(...) ->
receive
foo ->
...;
take ->
...;
quit ->
...;
end.
Tillämpad programmering ID1218
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Finite State Machine
closed(...) ->
receive
bar ->
...;
release ->
...;
quit ->
...;
end.
Tillämpad programmering ID1218
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Finite State Machine
-module(lock).
-export([start/0, take/0, release/0,
foo/0, bar/0, quit/0]).
start(Arg, ..) ->
:
spawn(fun() -> init(...) end).
init(...) ->
:
open(....).
Tillämpad programmering ID1218
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Finite State Machine
take(Lock) ->
Lock ! take.
release(Lock) ->
Lock ! release.
quit(Lock) ->
Lock ! quick.
Tillämpad programmering ID1218
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Finite State Machine
open(...) ->
receive
foo ->
...;
{take, Pid} ->
Pid ! ok,
...;
quit ->
...;
end.
Tillämpad programmering ID1218
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Finite State Machine
take(Lock) ->
Lock ! {take, self()},
receive
ok -> ok
end.
Tillämpad programmering ID1218
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Finite State Machine
take(Lock) ->
Ref = make_ref();
Lock ! {take, Ref, self()},
receive
{ok, Ref} -> ok
end.
Tillämpad programmering ID1218
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Finite State Machine
take(Lock) ->
Lock ! take.
release(Lock) ->
Lock ! release.
quit(Lock) ->
Lock ! quick.
Tillämpad programmering ID1218
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Finite State Machine
open(State) ->
receive
foo ->
Transf = state:foo(State),
open(Transf);
take ->
...;
quit ->
...;
end.
Tillämpad programmering ID1218
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Modululer
lock
Tillämpad programmering ID1218
state
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